Final answer:
Communicable diseases are infections that can be spread from person to person through casual contact, caused by pathogens like bacteria, viruses, fungi, and protozoa.
Step-by-step explanation:
A communicable disease that can be easily transmitted from person to person is a type of disease that falls under the category of diseases caused by various pathogens including bacteria, viruses, fungi, and protozoa. These diseases can be spread through casual contact such as touching similar surfaces, skin-to-skin contact, or through airborne transmission from coughs and sneezes. Infectious diseases like the common cold, influenza, and athletes foot are examples of communicable diseases. It's crucial to understand that not all diseases caused by fungi, viruses, or parasites are communicable, as some require more intimate contact for transmission. Therefore, the answer to the question is d. communicable.